1. Field of the Invention
The present invention relates to an EL display device and an electronic device including the EL display device.
2. Description of the Related Art
A transistor for driving a display element in a display device includes a silicon film or the like formed over a glass substrate or the like. Although a transistor including amorphous silicon has low field-effect mobility, it can be formed over a larger glass substrate. On the other hand, a transistor including polycrystalline silicon has high field-effect mobility, but it is not suitable for a larger glass substrate and used in a small or medium display device.
In a display device in which a light-emitting element such as an EL element is driven with the use of a transistor including polycrystalline silicon (EL display device), there is variation in threshold voltage and mobility among transistors including polycrystalline silicon in plural pixels. Patent Document 1 discloses a structure for reducing variation in threshold voltage and mobility among transistors.